California Code, Elections Code - ELEC § 14223

(a) Only members of the precinct board, and persons while signing their names on the roster, shall be permitted, during the hours within which voting is in progress, to sit at the desk or table used by the precinct board.

(b) Any person may inspect the roster while voting is in progress and while votes are being counted.  However, this shall not be done at a time or in a manner which will impede, interfere, or interrupt the normal process of voting.